In July and August 2016, I will be running two lab-based experiments. For one of them, I want to put 1-3 species of brown macroalgae in the flume tanks owned and operated by the Martone Lab at UBC but first needed to be sure that the algae are 'happy' in the flumes, as closed systems, for a period of 7-10 days. There are many ways to determine the health and happiness of macroalgae; for this trial, I was interested in monitoring their photosynthetic yield (Y), their change in biomass, and biomechanical tissue properties (e.g. modulus, toughness, strain).

Seven macroalgal species were collected: Pleurophycus gardneri, Agarum fimbriatum, Costaria costata, Egregia menziesii, Nereocystis leutkeana, Saccharina groenlandica, and Saccharina latissima. These were placed in two flumes set at two water velocities: 0.1 m per second and 0.6 m per second.

The macroalgae were left in the tanks for 10 days, after which the final biomass and PAM readings (photosynthetic yield) were re-measured. I also attempted to determine the biomechanical properties of the tissues but their were technical difficulties and the Instron ultimately ate the tissues without producing reliable results! While all algae had relatively high photosynthetic yields at the beginning and end of the trial (good!), some algae were thrashed in the high flow tank. The latter was not a surprise because the species that faired poorly are typically found in low flow environments.

Figure 1. Photosynthetic yields determined via pulse-amplitude modulation (PAM). Healthy photosynthetic tissues are typically in the 0.700's, as seen above. There is evidence of a minor reduction if Y values after 10 days (final values), but the reduction is minimal.

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Figure 2. The change in biomass for each species that was tested, represented as relative growth rates (RGR per day). Pleurophycus, Agarum, and Costaria are typically found in environments with lower flow, which is reflected by the loss or low accumulation of biomass in the fast flow treatment -- interestingly these had the highest biomass RGR in the slow flow treatments. The Saccharina species seem to love life in the flume!